The present invention relates to a lip sealing ring of elastomer material having an embedded metallic reinforcing ring and a sealing lip of a fluoroelastomer, and to a method of manufacturing such a ring.
Lip sealing rings, such as, in particular, sealing rings for rotating shafts or reciprocating rods usually are made of elastomer materials and contain embedded metal rings as reinforcements. In many cases, however, the sealing rings are subjected to high thermal and chemical stresses and in such cases the elastometric portions of the sealing rings are made entirely of fluoroelastomers which are known to be able to withstand high chemical and thermal stresses.
Due to the high cost of the basic fluoroelastomer material, however, the sealing rings made entirely of fluoroelastomers are comparatively rather expensive. It has therefore been proposed, in British Pat. No. 962,097, to make only the actual sealing lip portion on which the high thermal and chemical stresses are exerted, of the fluoroelastomer, while the remaining elastomeric region of the sealing ring is made of a more economical natural or synthetic rubber. Such sealing rings are much less expensive with respect to the elastomer materials employed, but problems have arisen in attaining a good connection between the two differing elastomer materials and possibly the metal ring inserts. Thus, the required adhesion is realized according to British Pat. No. 962,097 by separate process stages, in which the fluoroelastomer sealing lip is first vulcanized to the metal ring and then the preshaped remaining portion of, in this case, nitrile rubber is vulcanized on. Such two-stage vulcanization complicates the manufacturing process and in principle the cost advantage attained by the use of different elastomer materials is more than compensated, and the sealing ring becomes more expensive than a ring made of solid fluoroelastomers. On the other hand, good adhesion of the various materials to one another is an absolute requirement for proper functioning of a lip sealing ring.